Leaf rust found in Willamette Valley
Willamette Valley farmers are advised to check their wheat fields for a fungus that hasn’t typically been seen in the area for more than a decade.
Oregon State University Extension cereals specialist Mike Flowers recently notified growers that leaf rust has been found in several research plots and grower fields in the northern and southern regions of the Willamette Valley.
Leaf rust is generally a warmer-season rust pathogen that typically arrives later in the season.
“We’re seeing it about a month earlier than we would normally see it,” Flowers said.
Leaf rust has largely been absent for the last 10 to 15 years, but the relatively unusually warm and moist weather has allowed it to infect earlier, Flowers said.
Leaf rust has dark orange pustules that appear in a random pattern across the leaf, unlike the stripes and bright orange pustules of stripe rust, a more common wheat disease, according to Flowers.
Leaf rust has been found on the varieties Bobtail and Cara, which are typically less susceptible to stripe rust.
When temperatures get hot, stripe rust usually shuts down, Flowers said. Leaf rust doesn’t fare well in cold temperatures, but does well in warmer temperatures.
“If it gets into irrigated spring wheat fields, it will act a lot like stripe rust,” Flowers said. “It probably won’t be slowed down by warmer temperatures, whereas stripe rust might.”
Similar to stripe rust, a heavy infection of leaf rust reduces yield, he said.
“We don’t have a very good idea of the susceptibility of our varieties to leaf rust, because we generally don’t see it to a point where we can actually take notes on it,” Flowers said. “Generally, when it comes in, it comes in late enough that it doesn’t really cause any economic harm. So it’s not really been worth the time and effort to screen varieties for it.”
Most wheat in the Willamette Valley is past flowering, so fungicides aren’t likely to be economical. Flowers recommends an application if fields are heavily infected or have not flowered yet.
“I don’t think it’s worth controlling, it’s not a heavy enough infection to try controlling,” he said.
Flowers wants to be sure the industry is aware of the situation and can identify it if it comes up.
“I don’t think it’s a big concern,” Flowers said. “There is this pathogen out there they may or may not run across ... this is not something a lot of the younger field men have probably seen.”